On the horizon

Imagine parenting a newborn who stays awake 24/7 for several weeks after birth. Welcome to life as the mother of a bottlenose dolphin or killer whale.

A team of US and Russian researchers studying sleep patterns of these female sea creatures and their young found that, unlike other mammals, newborns do not sleep. The mothers do - but only briefly. Over time, both gradually reach - or return to - adult sleep levels. For newborns, the team says, cavorting beneath the waves all day every day may help them avoid predators. The ceaseless activity also may keep their body heat up until they develop sufficient layers of blubber to insulate them.

Sleep deprivation has been fatal to some lab animals, leading researchers to conclude that sleep is vital for brain and body development. Here, however, a lack of sleep seems no barrier to healthy development. "Our findings indicate either that sleep behavior may not have the developmental and life- sustaining functions attributed to it, or that alternative mechanisms have evolved in cetaceans," the team writes in Thursday's edition of the journal Nature.

El Niño brings unusually warm water across the tropical Pacific to South America every three to seven years, bringing drought to some regions and heavy rains to others. Now researchers have found what may be the mother of all El Niños. It spanned much of the period between 1.7 million and 5 million years ago, according to a study from the University of California at Santa Cruz.

That time span represents the last period when global average temperatures were warmer than they are today. That doesn't mean the world is headed for a superlong El Niño as the global climate warms, researchers say. But the results do suggest that the ocean-atmosphere system is capable of finding dramatically different "stable" states.

Three USCS marine scientists built a record of ancient sea-surface temperatures by examining shells taken from several locations in the tropical Pacific. The shells of tiny ocean-surface creatures called foraminifera contain certain chemicals that vary with the water temperature as they grow. The results appear in the current edition of Science.

Sizing up ancient wanderers

North and South America must have looked mighty lonely to those who crossed from Siberia to what is now Alaska as early as 14,000 years ago. If they could hold a reunion today, these ancestors to native Americans wouldn't fill two Greyhound buses, according to a new study out of Rutgers University.

Between 70 and 80 people formed the first colonizing group from Asia, says Rutgers biologist Jody Hey. He calculated the size by tracking subtle differences in DNA sequences for nine genes common to native Americans and native Asians. Previous studies used only one common gene. This made it hard to tell if the changes came from shifting demographics or from random variations in the gene's evolution. By using more genes, Dr. Hey was able to separate the true demographic changes from the "noise" of random evolution.

The wanderers split from an Asian population estimated at about 9,000. Hey notes that his approach represents a new tool for estimating not only the size of an ancestral population in an area, but the size of that population's founding groups as well. The work appears online in the current edition of the Public Library of Science - Biology.

Chickadees may be tiny, but they warn of looming predators with a mighty voice. In fact, chickadees have one of the most advanced sets of warning signals yet found in animals, scientists say.

Their alerts distinguish between flying predators and stationary or perched threats. The warnings also vary with a predator's size, according to a study led by University of Washington graduate student Chris Templeton.

The team recorded warning calls when different predators, including a cat and ferret, and 13 bird species, were tethered in an aviary containing the chickadees.

The predator garnering the most energetic warnings: a pygmy owl. Its small size apparently makes it more than a match for the agile chickadees in flight.

The team also found that many of the changes in calls take place outside the range of human hearing.

When the team played back the calls without the predators present, the chickadees' mobbing behavior changed based upon the size and type of the threat implied by the recording. The calls even attracted other bird species to harass the predator.

The experiment is described in the current edition of the journal Science.